1. Field of Invention
The present invention relates to the use of compounds which are present in the secretions of the Harderian glands of certain animals, e.g. rabbits, in the preparation of a medicament for treating “dry eye” or other ocular disorders. A further embodiment of the present invention relates to a method of treating a patient suffering from “dry eye” and related ocular disorders with said medicament.
2. Description of Related Art
The Harderian gland is a gland found within the eye's orbit which occurs in vertebrates (reptiles, amphibians, birds and mammals) that possess a nictitating membrane. The gland secretes fluid (mucous, serous or lipid) that varies between different groups of animals. Various reptiles, birds, and sharks, as well as mammals such as camels and polar bears, have a full nictitating membrane. It is often called a third eyelid. In many mammals, there is a small vestigial remnant of the nictitating membrane present in the corner of the eye. In some animals it acts as an accessory to the lacrimal gland, secreting fluid that eases movement of the nictitating membrane.
The gland may have several other functions, including that of a photoprotective organ, a location of immune response, a source of thermoregulatory lipids, a source of pheromones, a source of saliva, and/or a site of osmoregulation.
The Harderian gland in rabbits is related to the nictitating membrane (from Latin nictare, to blink), which is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten the eye while also maintaining visibility. In rabbits and rodents, the Harderian gland secrets non-polar lipids near the surface of the eye which mixed with the tears of the lacrimal gland. Rabbits do not suffer from “dry eye” as do humans. It is believed to be the lack of protective fluids of the Harderian gland may make humans more susceptible to “dry eye” and diseases associated with “dry eye.
Humans are subject to the development of damage to the cornea and conjunctiva as a result of insufficient tears or insufficient lubricating substances within the tears. This is a common problem increasing with age and more marked in women than men. Various wetting agents and solutions commonly known as “artificial tears” are only partially effective in protecting tissues in patients with “dry eyes”. Alteration, deficiency or absence of the tear film may lead to intractable desiccation of the corneal epithelium, ulceration and perforation of the cornea, an increased incidence of infectious disease, and ultimately, severe visual impairment and blindness.
Dry eye is a disease of the tears and ocular surface resulting in symptoms of discomfort, visual disturbance, and a tear film that inadequately protects the eye leaving potentially damaging conditions for the ocular surface. Keratoconjunctivitis is inflammation of the cornea and conjunctiva. Keratoconjunctivitis sicca (KCS) is chronic, bilateral desiccation of the conjunctiva and cornea due to an inadequate tear film.
Individuals suffering from tear film dysfunctions are diagnosed with keratoconjunctivitis (KCS), for example Sjögren's Syndrome or simply “dry eye”. These lacrimal abnormalities are subdivided into four general categories:
1. Aqueous tear deficiencies most frequently responsible for dry eye states, originating from lacirmal gland disorders including autoimmune disease, congenital alacrima, paralytic hyposecretion or excretory duct obstruction.
2. Mucin deficiency which is observed in conditions associated with trachoma, thermal and chemical burns, hypovitaminosis A.
3. Lipid abnormalities.
4. Diminished eyelid function. (See U.S. Pat. No. 6,107,289).
Evaporative keratoconjunctivitis sicca is caused by loss of the tear film due to abnormally rapid evaporation which is a result of an inadequate oil layer on the surface of the aqueous layer of tears. Symptoms may result from an abnormal oil in the tear film.
Aqueous tear-deficient keratoconjunctivitis sicca is caused by inadequate tear volume while evaporative keratoconjunctivitis sicca (more common) is caused by accelerated tear evaporation due to poor tear quality. Aqueous tear-deficient keratoconjunctivitis sicca is most commonly an isolated idiopathic condition in postmenopausal women. It is also commonly part of Sjögren's syndrome. It is secondary to other conditions that scar the lacrimal ducts due to trachoma. It may result from a damaged or malfunctioning lacrimal gland, HIV (diffuse infiltrative lymphocytosis syndrome), local radiation therapy, or familial dysautonomia. A subset of the dryness symptoms is expressed as Sjögren's syndrome, which is also a known “Sicca syndrome” and is a systemic autoimmune disease in which immune cells attack and destroy the exocrine glands that produce tears and saliva. Nine out of ten Sjögren's patients are women and the average age of onset is late 40s, although Sjögren's occurs in all age groups in both women and men. It is the second most common autoimmune rheumatic disease in the United States. Autoimmune rheumatic disorders include Rheumatoid arthritis A.
Patients suffering from dry eye report itching; burning; a gritty, pulling, or foreign body sensation; or photophobia. A sharp stabbing pain, eye strain or fatigue, and blurred vision may also occur. Some patients note a flood of tears after severe irritation.
Artificial tears are used to relieve temporarily the symptoms of discomfort associated with dry eye and sometimes blocking the nasolacrimal openings. Ideally the artificial tear or lubricant should provide lubrication and moisture to the tear film and protect the ocular surface.
Prior art compositions useful for administering medications into the eyes are generally effective, but many have the drawback of requiring frequent administration and are often rapidly washed away by the natural processes of the eye. The current prescribed therapeutic approach to managing KCS is the frequent application of artificial tear substitutes for lubricating the anterior eye surface. Frequent artificial tears and lubricants may cause visual blurring and alter the ocular surface and chemistry of the tear film on the ocular surface.
Hypotonic solutions used for ocular irritation may flood the ocular surface with water, enter the cells and produce a hypotonic artificial tear, which may leave the ocular surface with less water and more irritated than before application of the solution. Glycerol is a common osmotic agent and a humectant and ophthalmic lubricant. It is applied to the ocular surface to relieve irritation at concentrations of approximately 1%. Excessive addition of glycerol to the human eye may not provide extended benefits for ocular lubrication. A long term ophthalmic lubricant or vehicle, to protect the tear film and ocular surface is needed. The present invention discloses a method of treating “dry eye” with compounds found in Harderian gland secretions.